1. Field of the Invention
The present invention relates to a liquid crystal display device used in a monitor for a personal computer or the like.
2. Description of Related Art
Recently, in connection with popularization of personal computers using liquid crystal display devices, for example, a large-size and high-definition (high-resolution) screen has been strongly required in the market, and in order to satisfy this requirement, it is necessary to both enlarge a liquid crystal display portion and enhance the performance of various kinds of driving circuits at the same time.
FIG. 19 is a schematic diagram showing one example of a main part of a conventional liquid crystal display device. In FIG. 19, reference numeral 1 represents an active matrix type liquid crystal display panel, reference numerals 2-1, 2-2, 2-9 and 2-10 represent data driver ICs for outputting data signals to data lines formed on the liquid crystal display panel 1. The data drivers IC2-3 to IC2-8 are omitted from the illustration of FIG. 19.
Reference numerals 3-1 to 3-4 represent gate driver ICs for outputting gate signals to gate lines formed on the liquid crystal display panel 1, and reference numeral 4 represents a timing controller for receiving data signals, clock signals and synchronous signals, etc. from the main body of a personal computer and supplying various kinds of signals to the data driver ICs 2-1 to 2-10 and the gate driver ICs 3-1 to 3-4.
Reference numeral 5 represents a control circuit board on which the timing controller 4 is mounted, reference numeral 6 represents a wiring board equipped in association with the data driver ICs 2-1 to 2-10 and reference numeral 7 represents a wiring board equipped in association with the gate driver ICs 3-1 to 3-4.
Reference numeral 8 represents a data signal line for transmitting data signals output from the timing controller 4 to the data driver ICs 2-1 to 2-10, and reference numeral 9 represents a clock signal line for transmitting clock signals output from the timing controller 4 to the data driver ICs 2-1 to 2-10.
Reference numeral 10 represents a terminal circuit provided at the terminal of the clock signal line 9. (g) shows the circuit construction of the terminating circuit 10, reference numeral 11 represents a power supply line for supplying power supply voltage VCC (for example, 3.3V), reference numeral 12 represents a ground line for supplying earth voltage GND and reference numerals 13, 14 represent terminating resistors.
The data driver ICs 2-1 to 2-10 drive the data lines of the liquid crystal display panel 1 with the clock signals as a reference signal. However, in connection with the increase in screen size and the enhancement in screen resolution, the number of pixels has increased, and under the present situation, the speed of the clock signals must be increased in order to write data voltages to all the pixels. Therefore, the electromagnetic interference (EMI) problem has been induced by the increase of the speed of the clock signals, and thus it has been an important matter to take some countermeasure to this problem.
JP-A-2001-84053 (Patent Document 1) has proposed a technique for reducing electromagnetic radiation caused by clock signals. According to this technique, two-phase clock signals which are reverse to each other in phase are delayed to generate plural clock signals which are timely displaced in rise-up timing from one another, and the different clock signals thus generated are supplied to respective circuit blocks, thereby reducing the simultaneous switching number.
However, even when the technique disclosed in the Patent Document 1 is applied to the conventional liquid crystal display device shown in FIG. 19, the clock signal lines for transmitting the plural clock signals displaced in rise-up timing must be lengthened structurally. Therefore, there is a problem that it is impossible to effectively reduce the electromagnetic radiation due to an antenna design of the clock signal lines.